Epoxide compounds are known to be used with a curing agent and other additives to form an epoxy resin curable formulation or composition which can subsequently be cured to form a cured product or thermoset. Such epoxy resin compositions can be used in various applications, for example in the composites and infrastructure industries. For use in composites and infrastructure applications, curable epoxy resin compositions generally require a fast cure to achieve effective production of a cured thermoset article.
Heretofore, various aliphatic amines such as diethylenetriamine (DETA) and cycloaliphatic amines such as aminoethylpiperazine (AEP) have been used in curable epoxy resin compositions to instill fast cure properties to the curable epoxy composition. However, curable epoxy compositions based on the above known amines often suffer from surface defects such as carbamation, often referred to as “blushing”. The blushing problem leads to formation of a haze appearance in the resultant cured thermoset which is a big problem and an undesirable property for cured thermosets especially for use in the composites and infrastructure industries which require epoxy resin systems that provide a cured product that does not blush or does not exhibit a “greasy” (e.g., “sticky” or “tacky”) surface.
Generally, the blushing phenomena can occur as the result of the active hydrogens on the known aliphatic amines and cycloaliphatic amines reacting with water (H2O) and carbon dioxide (CO2) components existing in air. The surface defects (e.g. blushing or carbamation) of thermoset articles detract from the appearance of the final thermoset article, and such defects can lead to the reduction of mechanical properties such as reduced glass transition temperature (Tg) or tensile strength due to the consumption of active hydrogen of the aliphatic amines and cycloaliphatic amines, i.e. blushing.
In the known art, some solutions to correct the above surface defects have been attempted. For example, sterically hindered amines such as trimethyl hexamethylene diamine (TMD) and polyetheramines such as Jeffamine™ can be used as substitutes for the known aliphatic amines and cycloaliphatic amines in curable epoxy resin compositions. However, the use of sterically hindered amines and other known materials such as polyether amines, generally results in other undesirable problems such reducing the curing speed of the curable composition, and/or lowering the thermo resistant properties of the curable composition. Furthermore, the current high cost of the known amines or the unique commercial resource of products such as TMD makes the known amines for use as curing agents in curable epoxy resin compositions highly undesirable.
Other known art provides various curable compositions with varying disadvantages. For example, JP2004346246A discloses a curable composition which includes an epoxy resin, an aliphatic tricarboxylic acid as a curing agent, and an organic solvent. The curable composition of JP2004346246A does not use an amine curing agent; therefore, the curable composition has low thermo resistance and low base resistance properties.
JP2004244430A discloses a water dispersible, epoxy group-containing polymer and a curing agent. The curing agent is a water-soluble aliphatic tricarboxylic acid. The curable composition of JP2004244430A does not use a specific phenol novolac as an accelerator; therefore, the curable composition has a slow hardness build-up property.
CN101585958A discloses a composition for preparing artificial stone including 100 parts of resin and 25-50 parts of a curing component, where the resin can be bisphenol F glycidyl ether, bisphenol F epoxy resin, and reactive diluents. The curing component is obtained by mixing non-reactive diluents, aliphatic amine, alicyclic amine, reactive diluents and polyetheramine.
FR1581068 discloses a hardener for an epoxide resin, where the hardener is an aromatic amine dissolved in a liquid phenol, the amine being 10% to 50% by weight. The curable composition of FR1581068 has a blushing problem.
Heretofore, phenalkamines or Mannich base products are known to be used in curable compositions. For example, US20090259003A1 discloses the use of Mannich base products of an aldehyde compound and a phenol compound. The curable composition of US20090259003A1 has an undesirable high viscosity.
WO200001659 discloses Mannich based reaction products-phenalkamines obtained by combing cardanol with at least aromatic or alicylic polyamine and at least one aldehyde compound. The curable composition of WO200001659 has an undesirable high viscosity.
WO2009080209A1 discloses a curing agent for epoxy resins, the curing agent including a phenalkamine blended with a salted polyamine or a salted polyamine-epoxy adduct. The curing agent described in WO2009080209A1 suffers from the disadvantage of having a high viscosity phenalkamine.
EP2108668A1 and EP1914257A1 disclose a composition including Mannich base derivatives of N,N′-dimethyl secondary diamine polymer. The amine-epoxy composition disclosed in EP2108668A1 and EP1914257A1 has a high viscosity phenalkamine.
Other curable compositions known in the art include, for example, a solvent-free ambient-temperature curable composition disclosed in US20060089432A1. The curable composition of US20060089432A1 does not use an epoxy resin; and therefore, the curable composition disadvantageously has limited application without an epoxy resin.
JP2003147191A discloses an aqueous-resin composition containing acetoacetic ester compound (A) and autoemulsified type amine curing agent (B). Disadvantageously, the composition of JP2003147191A cannot be used in conventional epoxy resin-related applications.
KR2010095529A discloses friction material-containing products such as clutch plates and brake shoes. The composition of KR2010095529A disadvantageously cannot be used in conventional epoxy resin-related applications.
US20090298960A1 discloses a composition containing an epoxy resin, a phenol compound (solid at room temperature), a polyether amine, a propellant (blowing gent), a curing agent and a filler for manufacturing structural foams. When the curable composition of US20090298960A1 uses a conventional aliphatic amine curing agent, the curable composition suffers from the disadvantage of blushing.
US20100048827A1 and US20100048954 disclose an amine composition used in manufacturing an article such as a coating. The amine composition comprises N,N′-dimethyl-meta-xylylenediamine (DM-MXDA), at least one multifunctional amine having at least 3 active amine hydrogen, and optionally plasticizer or solvent. The amine composition of US20100048827A1 and US20100048954 suffers from the disadvantage of having high viscosity and slow hardness build-up properties.
JP2011213983A discloses a condensate obtained with condense polyamine, a phenol and an aldehyde. The condensate of JP2011213983A suffers from the disadvantage of having a high viscosity.
US20080188591A1 discloses curing agent compositions comprising the reaction product of alkylated polyalkylene-amine compounds and polyalkylene polyether polyol modified polyepoxide resins as waterborne amine-epoxy compositions. The curing agent compositions disclosed in US20080188591A1 suffer from the disadvantage of having a slow hardness build-up property.
US20100298505 discloses a liquid resin composition including a novolac resin, a reactive diluent and optionally a crosslinking agent. The crosslinking agent is chosen from compounds incorporating a hydroxyl or aldehyde functional group, heterocyclic compounds that have a structure incorporating a nitrogen atom and an oxygen atom separated by a carbon atom, nitroacetals and nitrones, tris(hydroxymethyl)nitromethane, glyoxal and 2,2-dimethoxyethanal. The composition of US20100298505 disadvantageously cannot be used in conventional epoxy resin-related applications.
US20100270495A1 discloses a thermally curable liquid resin composition for manufacturing abrasives that includes an epoxy resin having two epoxy groups and a reactive diluent. The composition includes a crosslinking agent chosen from compounds incorporating at least one amine, hydroxyl, aldehyde or carboxylic functional group, and heterocyclic compounds that have a structure incorporating a nitrogen atom and an oxygen atom separated by a carbon atom. The curable composition of US20100270495A1 suffers from the disadvantage of having a slow hardness build-up property.
What is needed in the epoxy industry is an epoxy curing agent and an epoxy curable formulation for manufacturing thermoset resin product, wherein the epoxy curable formulation, among other advantages, (1) has no problems with blushing, (2) has a balance of properties, and (3) is useful in composites and infrastructure applications.